Elijah had no good reason to tell you exactly how the bomb collars worked or how he modified them as such. There is a certain willing suspension of disbelief that goes into Dead Money, much like
nearly every other part of the game, including the lore and background. Picking apart an aspect of the DLC simply because it was different and difficult makes about as much sense as complaining about giant mutated ants, or people turning into dessicated corpses that heal from radiation. Nothing requires you to complete that DLC, anyway.
I just found out that some seemingly useless items can be turned in to NPCs to be converted into useful crafting mats (mugs and dinner plates Muggy in OWB). Are there any other "junk" items I should be saving/looking out for when looting?
Old World Blues was the best type of crafting base, since you could turn junk into useful materials, such as metal and duct tape from clipboards, electronics from toasters, wonderglue and syringes from mugs, giving everything but wrenches for weapon repair kits. Don't forget basically every type of plant, which can be turned into
Soylent Salient Green that can subsequently be turned into more useful types of plants, which combined with the syringes can mean easy stimpacks.